This section provides background information related to the present disclosure which is not necessarily prior art.
Heating, ventilation, and air conditioning (“HVAC”) units for vehicles generally include a housing and plurality of flues that direct air through the housing and to various components of the HVAC unit, such as different outlets or heat exchangers for example. The HVAC unit generally includes at least one door within the flues that can be moved between multiple positions to selectively control the amount of air that passes through the various components. In some intermediate positions of these doors a relatively small cross-sectional flow area between the door and the housing can be created, which can result in a relatively high velocity of the air through that area. It has been found that the passage of the air through these narrow spaces when doors are nearly closed can cause an undesirable noise, such as a whistle for example.